Electronically-Controlled Tankless Water Heater with Pilotless Ignition

ABSTRACT

A rapid recovery tankless water heater operates by means of an electronic controller or card that regulates the operation of each of the system components, thereby optimizing gas consumption and minimizing the emission of gas pollutants. A multi-burner only ignites when certain conditions or predefined requirements in the electronic controller logic are met. Other factors contributing to improved water heater efficiency are: a) the water tank design which at the bottom has a water chamber surrounding the combustion chamber, and b) the use of a finned heat exchanger, which together with a core, successfully utilizes most of the thermal energy contained in the combustion gases. An air deflector device stops the entry of air currents at the top of the heater, thus stopping potential flame reversing and even flame extinction in the multi-burner.

FIELD OF INVENTION

This invention refers generally to water heating equipment thatmaximizes its efficiency while reducing heat loss through use of afinned tube-type heat exchanger and water chamber surrounding thecombustion chamber. This water heater is able to provide a constantsupply of hot water and is controlled electronically.

INVENTION BACKGROUND

Instant or rapid-recovery tankless water heaters are currently availableto meet the constant demand for hot water with the greatest possible gasfuel savings. In the case of instant-type heaters, however, the problemis that they must perform at minimum hydraulic operating pressure. Inaddition, in regions with an ambient temperature that can fall belowzero degrees Celsius, the water contained in the coil of these types ofheaters can freeze, and, due to their respective volumetric expansion,can cause coil breakage and consequently ruin the equipment. The PCTWO120071057864 patent publication offers an alternative for solving thefrozen water problem in this type of heater, although the problem ofminimum hydraulic operating pressure still remains, whereby instant-typeheaters continue to be inadequate for use in most existing hydraulicinstallations, causing in many instances the necessary modification orintegration of other components in the system for proper operation andincreasing equipment cost.

The creation of a water heater similar to the one described in theprevious paragraph responds to the need for constant water pressure inhydraulic systems, gas savings, and adaptability to different types ofhydraulic systems in order to meet a constant demand for hot water.

The rapid-recovery tankless equipment mentioned in U.S. Pat. Nos.7,982,164 and 7,985,943 do not require a minimum operating hydraulicpressure for proper functioning, as they are not the instant type.Nevertheless, the heaters described in the aforementioned patents use anelectromechanical flow detector to send the hot water demand signal tothe electronic controller. This flow detector presents a point ofconvergence for scale build-up, and when used in regions where waterfrom the hydraulic network contains high salt concentrations, flowdetector operation can be affected, altering equipment operation.

Invention Summary This invention's water heater eliminates the need foran electromechanical flow detector since it uses a system with twotemperature sensors, one at the cold water inlet and the other at thehot water outlet. Thus, we can deduce that when the unit registers a 4°C. difference between the two temperature sensors, water is admitted.This water heater uses an electronically-controlled, ionized ignitionsystem which gives the command to ignite under the following conditions:

a) Whenever a flow signal and the temperature sensor located at the hotwater outlet detect a temperature below the maximum shut-off temperatureprogrammed in the electronic controller.

b) It likewise will ignite when the temperature detected by both sensorsis less than a preset value in the electronic controller as the minimumignition temperature.

In this way, the water heater will only ignite when hot water is neededaccording to the programming in the electronic controller.

Objects and advantages of the invention are set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

This invention's water heater has been designed to include thefollowing: a corrosion-resistant water tank which is sufficientlyelongated at the bottom to create a water chamber surrounding thecombustion chamber located over a multi-burner so that heat loss to theexterior of this area is minimized. A fin-type heat exchanger at the topof the tank allows capture of most of the thermal energy contained inthe combustion gases and transferring it to the water contained in thetank. A 8.7-13.0 kW burner is supplied by gas from an electrovalvesystem. A bimetallic temperature detector functions to avoid overheatingthe water inside the equipment. Two temperature sensors are located atthe cold water inlet and the hot water outlet, respectively. A firstelectrode generates a spark for igniting the burner and a secondelectrode detects the change in current produced at the first electrodedue to ionization following burner ignition. An electronic controllerthat, when the hot water demand conditions are met and/or the watertemperature in the heater is less than the preset temperature, sendscurrent to the first electrode so that it is able to generate the burnerignition spark. An electrovalve system allows gas to flow safely to theburner once the electronic controller has sent the current to generatethe spark in the first electrode. A screen in direct communication withthe electronic controller allows the user to observe the state of thewater heater at any given time.

This invention's entire set of components allows the water heater tooperate while ensuring the safety of the user and of the water heateritself and maximizing gas fuel economy, without a permanently lit pilotlight.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an overall view of this invention's water heater.

FIG. 2 shows an exploded view of the main components: water tank, drainvalve, outer body, electrovalve system, electronic controller and airdispersion device.

FIG. 3 is a cross-sectional view of the top of the heater.

FIG. 4 is a cross-sectional view of the bottom of the heater.

FIG. 5 is a view of the card or electronic controller.

DETAILED DESCRIPTION OF THE INVENTION

Reference is now made to particular embodiments of the invention, one ormore examples of which are illustrated in the drawings. Each embodimentis provided by way of explanation of the invention, and not as alimitation of the invention. For example, features illustrated asdescribed as part of one embodiment may be used with another embodimentto yield still a further embodiment. It is intended that the presentinvention include these and other modifications and variations.

This invention's water heater (1) shown in FIG. 1 is designed towithstand a pressure greater than 1.0 MPa. The steel water tank (2) isporcelainized on the areas in contact with water to prevent corrosion.

The cold water inlet (3) is located to the upper-right of the water tank(2), likewise, the hot water outlet (4) is located at the upper left ofthe tank (2). Additionally, on the lower part of the water tank (2),there is a coupling that connects the water tank (2) to the exterior,allowing draining and cleaning of the water tank (2) through aconveniently placed valve (6).

An electrovalve system (8) supplies gas to a multi-burner (7) providingthe energy needed to heat the water. The capacity of the multi-burner(7) depends on the size of the equipment, which in turn will depend onuser requirements.

The multi-burner (7) and an electrovalve system (8) regulate the safeflow of gas. This electrovalve system (8) is protected by a screen (9)from thermal radiation. The electrovalve system (8) is connected to themulti-burner (7) to enable the transfer of gas fuel between components.The electrovalve system normally is closed until the electroniccontroller (10) sends the signal to open once the following hot waterdemand and/or water temperature conditions have been met:

-   -   a) Whenever a flow signal and temperature sensor located at the        hot water outlet (12) detect a temperature less than the maximum        preset shut-off temperature on the electronic controller (10);        or    -   b) Whenever the temperature detected by both temperature sensors        (11 and 12) is less than the preset value on the electronic        controller as the minimum ignition temperature.

The electronic controller (10) sends the signal to close off theelectrovalve system (8), thus stopping the flow of gas fuel to theburner when both of the previously mentioned conditions have not beenmet.

The temperature sensors located at the cold water inlet (11) and the hotwater outlet (12) are inserted in a connection made of brass, bronze orother corrosion resistant material and these, in turn, are joined to awater tank at the cold water inlet and hot water outlet, respectively.

The two cables for each of the temperature sensors (11 and 12) must bein contact in the end inside the water tank, with the opposite endconnecting to the electronic controller (10), just as with the gas feedelectrovalve system (8). There is a bimetallic safety device (13) on theside of the temperature sensor at the hot water outlet (12), thatoperates whenever the water tank (2) overheats, interrupting the flow ofcurrent to the electronic controller (10). This bimetallic safety deviceallows suspension of system operation in case the water temperatureexceeds a preset value. Thanks to its configuration, the temperaturesensors (11 and 12) allow the electronic controller (10) to identify thecondition of the demand for water whenever there is 4° C. differencebetween both temperature sensors (11 and 12). Therefore, the waterheater (1) only restarts operation when the temperature in thebimetallic safety device (13) is less, e.g., 4° C., than the specifiedsafe temperature.

The electronic controller (10) regulates the operation of the differentwater heater components, and when it receives a temperature signalindicating a difference of more than 4° C., for example, between thetemperature sensor at the hot water outlet (12) (T_(s)) and thetemperature sensor at the cold water inlet (11) (T_(e)) (T_(s)−T_(e)>4°C.), it sends a direct current signal to the ignition electrode (14)shown in FIG. 4 in order to generate the electric spark for lighting themulti-burner (7).

The ignition electrode (14) is situated no more than 4 mm above one ofthe burners of the multi-burner (7). After 3 seconds and with theelectric spark in operation, the electronic controller (10) sends asignal to the electrovalve system (8) for sequential opening of theelectrovalves of this system (8) so that gas is able to flow to themulti-burner (7). Once the multi-burner (7) ignites, the ionizingelectrode (15), (shown in FIG. 4) and situated no more than 4 mm aboveone of the burners in the multi-burner (7), detects the flame by meansof an ionization process and sends the signal to the electroniccontroller (10).

If the flame signal is not received by the electronic controller (10)within 5 seconds, or if the signal is intermittent during the sameperiod of time, or if the burner of the multi-burner (7) goes out at anytime, the electronic controller (10) sends a signal to the electrovalve(8) feeding gas so that it will close immediately and block the waterheater operation (1) for a period of 10-15 seconds to allow thedissipation of gas in the combustion chamber (16) and performance of anelectronic check of the components connected to the electroniccontroller (10).

After the previously mentioned period of 10-15 seconds, a water heater(1) restart is performed until obtaining of a continuous signal of aflame in the multi-burner (7). Should this signal not be detected aftera total of three attempts, the electronic controller (10) will send asignal for an error message to appear on the screen (17), indicatingthat as a safety measure the system has been temporarily blocked.

Once the electronic controller (10) detects the signal indicating that aflame exists, the water in the water tank (2) will heat up until thetemperature sensors at the cold water inlet (11), T_(e), and hot wateroutlet (12), T_(s), send a signal to the electronic controller (10)indicating that the specified temperature has been reached. In turn, theelectronic controller (10) sends a signal to close the gas-fedelectrovalve system (8).

Although the ignition cycle reactivates, it shuts off when any of thepreviously mentioned conditions occur.

The electronic controller (10) is supplied electrically from a powersource (18) using any combination of replaceable batteries, rechargeablebatteries or direct connection to an electric grid, as shown in FIG. 2.In turn, the electronic controller (10) distributes the current supplyto the various components to which it is connected.

The water chamber (19) shown in FIG. 4 surrounds the combustion chamber(16), minimizing heat loss toward the sides of the combustion chamber(19), and under it are the multi-burner (7) and its support (20). On theinside face of the water tank (2) is a heat exchanger (21), shown inFIG. 3, the front of which is made up of a set of fins, which capturemost of the thermal energy in the combustion gases, although they giveup this energy later to the water in the tank (2), that is, through thesuccessful transfer of 80%-95% of the thermal energy in the combustiongases to the water in the tank.

In the center of the heat exchanger (21) is a core (22) in the shape ofa cylindrical vessel (see FIG. 3), whose function is to retard andredirect the combustion gases in their outbound path, forcing them topass through the heat exchanger fins (21).

As seen in FIG. 3, the exterior of the water tank (2) is thermallyinsulated through the application of an insulator (23) or low thermalconductivity material covering, such as polyurethane, mineral wool,ceramic fiber, fiberglass or any other known medium.

The water heater (1) has an exterior plate body (24) shown in FIG. 2,which is covered with a rust-resistant electrostatic paint to improveproduct aesthetics, and it ensures that the insulator (23) stays aroundthe water tank (2), and protects both the insulator (23) and the watertank itself (2) from the environment.

The exterior plate body (24) shown in FIG. 2 has a housing for theelectronic controller (10) and openings on the base in the area wherethe multi-burner is located (7) for the intake of air needed forcombustion.

The electrovalve system (8), along with the power source (18), islocated on the left side of the exterior plate body (24). Both theelectrovalve system (8) and the power source 18) are protected from heatradiation from the multi-burner (7) by a pair of screens (9).

As can be seen in FIG. 5, the electronic controller (10) contains aseries of buttons for the user to operate the heater.

The valve (6) located on the lower right side of the equipment allowsdrainage and cleaning of the water tank (2).

The air baffle (25) shown in FIG. 2 stops air currents from entering thetop of the heater, potential flame reversing, and even flame extinctionin the multi-burner.

Most of the time, the water heater (1) is not in operation, except whenany of the previously mentioned ignition conditions occur. For thisreason, it provides a reduction both in gas consumption and, as aconsequence, in the emission of gas pollutants into the environment.

Modifications and variations can be made to the embodiments illustratedor described herein without departing from the scope and spirit of theinvention as set forth in the appended claims.

1-5. (canceled)
 6. A rapid-recovery tankless water heater, comprising: amulti-burner disposed below a combustion chamber; a corrosion resistantwater tank having a water chamber surrounding the combustion chamber; afinned heat exchanger configured around a center core in an upper partof the combustion chamber, the core serving to redirect combustion gasesthrough the heat exchanger; and electrovalve configured with themulti-burner to control gas flow to the multi-burner; an electroniccontroller, the electrovalve in communication with the electroniccontroller; a bimetallic safety device disposed to detect watertemperature within the water tank, the bimetallic safety device incommunication with the electronic controller to cease operation of thewater heater upon detected water temperature exceeding a preset value;an ignition electrode in communication with the electronic controller toignite the multi-burner; an ionized electrode in communication with theelectronic controller to detect ignition of the multi-burner; a firsttemperature sensor at a cold water inlet to the water tank, and a secondtemperature sensor at a hot water outlet from the water tank, the firstand second temperature sensors in communication with the electroniccontroller to generate a hot water demand flow signal upon a presenttemperature differential between the first and second temperaturesensors; and an air baffle configured atop the water tank to minimizeair currents from entering the combustion chamber.
 7. The water heateras in claim 6, wherein the electronic controller is configured to sendan ignition spark signal to the ignition electrode under the followingconditions: (a) when there is a hot water demand flow signal andtemperature sensed by the second temperature sensor at the hot wateroutlet is less than a preset cutoff temperature; or (b) temperaturedetected by both of the first and second temperature sensors is lessthan a preset minimum ignition temperature value.
 8. The water heater asin claim 7, wherein the electronic controller is configured to send asignal to the electrovalve to stop gas flow to the multi-burner whenboth of the ignition signal conditions are not met.
 9. The water heateras in claim 6, wherein the electronic controller is configured to send asignal to the electrovalve to open and let gas flow to the multi-burnerafter a preset time delay from generating an ignition spark signal tothe first electrode,
 10. The water heater as in claim 9, wherein theelectronic controller is configured to send a single to the electrovalveto stop gas flow to the multi-burner under any of the followingconditions: (a) an ignition signal is not received from the secondelectrode after a preset time from generation of the ignition sparksignal to the first electrode; (b) an ignition signal received from thesecond electrode is intermittent during a preset time from generation ofthe ignition spark signal to the first electrode; or (c) themulti-burner goes out at any time.